Lochinvar Power-Fin Designer's Manual page 26

Designer's Guide / Power-fin Water Heater
This layer of lime scale can become so thick it will interfere with the heat transfer process.
Normally, heat is transferred efficiently from the flame through the copper and into the water. The
lime scale becomes a layer of insulation between the copper and the water. If the copper can't
instantly release the heat into the water, then the copper will overheat. This leads to a failure of
the copper and ultimately, the entire heat exchanger.
Warning
FAILURE OF THE HEAT EXCHANGER DUE TO LIME SCALE BUILDUP IS A NON-WARRANTABLE
FAILURE.
Here is why flow rate is important to lime scale. If the flow rate is too low, the calcium has a
chance to adhere to the copper. But if we flow the water fast enough, the calcium doesn't get a
chance to adhere to the tube. In addition, at the proper flow rate, the water creates a scouring
action that tumbles along the ribbed interior of the copper tube, keeping it clear of lime scale.
Therefore, too low a flow rate is bad. Conversely, too high a flow rate can also damage the
tubes. At too high a flow rate, the scouring action of the water becomes so aggressive that it
chips away at the copper tube, eroding the tube and causing tube failure. That's not warrantable
either.
Temperature Rise Chart
Copper Heat Exchanger
Model
Number
PFN0502PM
PFN0752PM
PFN1002PM
PFN1302PM
PFN1501PM
PFN1701PM
PFN2001PM
COPPER-NICKEL HEAT EXCHANGERS
These flow rates will deliver the proper temperature rises for lime scale free operation in the
copper-finned tubes that are standard equipment on all Power-fins. For water that is just outside
the specified range, the Power-fin water heaters can be factory trimmed with Copper-Nickel heat
exchangers.
90% copper, 10% nickel, the Copper-Nickel finned tube is a harder alloy than pure copper. With
a harder alloy, we can flow the water through the heat exchanger at a greater speed. If you have
water chemistry in the following range, you can use a copper-nickel exchanger instead of a water
softener. The higher flow rates for the Copper-Nickel heat exchanger are 25% faster.
WATER CHEMISTRY
While flow rate has been our main focus, there is
the idea of water chemistry, the amount of calcium and Total Dissolved Solid in the water. Now,
let's add Ph to the list and look at them closely.
Temperature
Rise °F
11
17
23
30
28
32
38
a companion concept to mention. We return to
26
LOCHINVAR CORPORATION
300 MADDOX SIMPSON PKWY
LEBANON, TN 37090
www.lochinvar.com
Temperature Rise Chart
Copper-Nickel Heat Exchanger
Model Temperature
Number Rise °F
PFN0502PM
PFN0752PM
PFN1002PM
PFN1302PM
PFN1501PM
PFN1701PM
PFN2001PM
9
14
18
24
22
26
30